Bad temp sensor?

[Lunduser]

I believe one of the temp sensors is bad on my 1990 Evinrude 90HP outboard. Do I have to pull the head to change the sensor? It sounds the overheat horn, but using an infra-red heat gun, the temperature looks OK.

 

[F_R]

Remove the thin water cover off the head, not the whole head.

 

[Lunduser]

Thanks for the info!

 

[Crosbyman]

check the sensor wire for chaffing/grounding.

 

[Lunduser]

The alarm sounds after about 15 minutes and unplugging that sensor turns it off. It is just tripping at too low of a temperature.

 

[tphoyt]

What temp is it tripping at and where are you taking that temp from?
Do you plan on replacing the sensor?

 

[Lunduser]

There are two sensors, one on each side of the motor. I was checking the temperature of the top of the head with an infra-red temperature gun. Both sides were about 140 degrees. Unplugging the left sensor turned the horn off. I am going to order a new sensor and gasket. That should fix my problem.